Many different so-called "spill-proof" containers are generally known, and their constructions and functioning differ from each other in numerous ways. The disclosure of U.S. Pat. No. 4,714,174 issued in the name of Williams, for instance, relates to a spill-proof container useful for holding dry, granular foodstuffs, and is not well-suited to use as a drink container.
U.S. Pat. No. 4,869,390 issued to Kennedy discloses details of a non-spill container for liquids that is basically comprised of an interior having two contiguous portions, one above the other, but such are not effective to fully contain against spillage of that portion of the contained liquid that is in the container lower interior portion and that volume-wise is greater than the volume of the container interior upper portion.
Also, U.S. Pat. No. 5,082,245 issued in the name of Kast, and assigned to General Electric Company, discloses a spill-proof check valve apparatus suitable for use in connecting two fluid passageways but such does not relate to, or appear suitable for use in, a drink container.
See also U.S. Pat. No. 5,309,924, which was issued in the name of Peabody and which pertains to a spill-proof blood collection device.
I have discovered a drink container assembly construction that I believe has a substantial spill-proof characteristic and that is relatively non-complex and easy to fabricate.